Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2005-11-22
2005-11-22
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S112030, C369S120000
Reexamination Certificate
active
06967916
ABSTRACT:
An optical head apparatus capable of stably obtaining a detection signal of spherical aberration even with a high density optical disk. A spherical aberration error signal is obtained by: dividing the returning light from the optical disk into a transmitted light and a diffracted light; reproducing information with the transmitted light having a larger amount of light while dividing the diffracted light having a small amount of light into two regions, i.e., region near the optical axis and a region distant from the optical axis; determining amounts of focus deviation in respective regions as focus error signals; and taking the difference signal therebetween. Thus, it is possible to detect the amount of spherical aberration with the SN ratio of the information reproducing signal kept at high level.
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Kadowaki Shin-ichi
Komma Yoshiaki
Nishino Seiji
Sano Kousei
Yasuda Akihiro
Hamre Schumann Mueller & Larson P.C.
Huber Paul W.
Matsushita Electric - Industrial Co., Ltd.
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